Bicycle Top Tube Adapter




Many hitch-mounted bike racks require a flat top tube. This is a top tube adapter to fit a mountain bike to a hitch-mounted bicycle rack. The cheapest one I've found is $20. I thought it would be simple to make with household junk and $7 worth of pins.

This is my first Instructable, feel free to comment.

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Step 1: Parts and Tools

Most of this was found around the house...

Segment of chain-link fence tubing (PVC pipe would've been much easier if available)
2 Chainlink fence tensioning brackets
Electrical Tape
2 Locking wire pins (about $3.50 each at Lowe's, in the same cabinet as Clevis pins)

Drill Press
Dog (gotta have a good distraction)

Step 2: Measure Twice, Cut Once

First, measure the tube length you'll need between the headset and seatpost, leave a little room for play. Mark the pipe with the needed length and stick it in your vice. Cut the section of fence tube to length. File sharp edges and wrap ends in a couple layers of electrical tape to protect paint and carbon fiber parts.

Step 3: Hammer It, Bend It, Make Holes in It

Take the fence tensioners and flatten them both out. Make sure to be careful, hold them tight and wear ear protection if using a metal surface to flatten them.

Next, measure the diameter of your headset and seatpost. Mine were about 1-1/2". Leave a little extra room and bend the flattened tensioners into a nice U-shape. I used a vice and shovel handle to keep the bend from getting a point. Wrap them in electrical tape if you want to protect your expensive bike parts.

Don't forget to cut the tape out of the pre-drilled holes in the tensioners. Your pins will go through these

Step 4: Puncturing Your Pipe

Set the pipe up on your top tube, and using rubber bands, place your U-shaped brackets where you want them. Mark through the holes in the U-brackets to the pipe for where you need to drill holes. Find a drill bit slightly larger than your pins, use your punch to make dimples at the starting points and go to your neighbor with the drill press. Drill holes through both sides of the pipe to keep them even. Make sure you securely fasten the pipe before you start drilling. After the first set of holes is done, use a LONG rubber band to go around the pipe and mark the second set of holes; this will insure all the pins wind up on the same plane.

Step 5: Voila!

Assemble the adapter, attach it to your bike. Now stick your bike on your rack and go find a new trail!


If you have thick PVC, use it. It is easier to drill through than the metal. Just make sure it doesn't flex too much with the weight of your bike.

Make sure your locking pins secure very well, I think i should've gotten longer ones to insure they don't vibrate open.

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13 Discussions


5 years ago on Introduction

Great Instructable!. However, I have a suggestion. Electrical tape lasts only a few uses, but it can be substituted with old inner tubes. You can wrap strips of inner tube instead. Before wrapping, just coat one side of the strip with a thin film of patch cement, the same glue used to patch inner tubes. This will also provide more cushioning for the delicate finish of your bike.


8 years ago on Step 5

Sweet ride! Is it a 29er? Good job on the top tube, you saved me $40 on the yakima version of it. Thanks!

I know this is a year old post, have you made any improvements?


10 years ago on Introduction

Thanks for the idea. I ended up using a car club that had both ends shaped in a 'U' configuration. One end was attached to the seat post and the other end on the handle bar post and part of the handlebar. When adjusted and locked, this also kept the bike straight. When taken off the bike once you reach your destination, you can use it on your steering wheel. These older model car clubs can be bought for around $3-5 at garage sales or thrift stores.


10 years ago on Step 5

Thanks for this great idea. You saved me $20 as I had all the parts to build this already.


10 years ago on Step 5

I'm not sure i would trust PVC has a tendancy to get brittle with UV exposure, and the last think you want is your expensive bike all over the road behind your car. Most bikes with the curved or odd top tubes (aside from ladies bikes) are heavier full-sussers. Stick with metal to be safe!


10 years ago on Step 5

great idea. you should market that sucker.


10 years ago on Introduction

Sweet bike, even for a full suspension, maybe its the sweet paint job.